It is like Daniel going into the lions' den, though Professor Richard Dawkins might not appreciate the biblical comparison. Britain's leading atheist is spearheading a campaign in America to challenge the dominance of religion in every day life and in politics, insisting that the millions of US godless deserve to be heard too.

Atheists in the US "have been downtrodden for a very long time. So I think some sort of political organisation is what they need", he said.

Maybe David and Goliath would be a better analogy. Religion is palpable in US schools, places of work and public institutions. God is invoked by soldiers and politicians in a way that would seem inappropriate in Britain. George Bush used God as one of the reasons for invading Iraq. In Congress, where godlessness can equate with being unelectable, only one representative, Pete Stark, is prepared to admit to being a non-believer.

According to a study published last year by the University of Minnesota, Americans distrust atheists more than any other minority group, including homosexuals, recent immigrants or Muslims.

Now the best-selling author of The God Delusion and chair of public understanding of science at Oxford has set up an organisation to help atheists round the world, including the US.

In an interview with the Guardian, he said: "When you think about how fantastically successful the Jewish lobby has been, though, in fact, they are less numerous I am told - religious Jews anyway - than atheists and [yet they] more or less monopolise American foreign policy as far as many people can see. So if atheists could achieve a small fraction of that influence, the world would be a better place."

His organisation, established two months ago, complete with T-shirts bearing a large red A, is the Out Campaign. "It does not mean outing, definitely not ... we want to encourage people to come out because there is a big closet population of atheists who need to come out."

His estimates, which square broadly with official data, show that atheists in the US account for about 10% of the population. "I have had many letters from people saying 'I don't dare give my opinions. I am afraid of my family. I am afraid of my wife, I am afraid of my husband. I am afraid of my work people. I am afraid of being fired'."

Prof Dawkins appeared as one of the stars of the Atheist Alliance convention in Crystal City, Virginia, at the weekend.

He admitted he was "a little bit hesitant" about being an Englishman talking to Americans and he showed "a certain amount of deference" when asked about US politics. "But I think that this country is so powerful and what goes on politically here is so enormously influential, the rest of the world is entitled to have a say. We don't get the vote here but I think people are entitled to express an opinion."

Although religious groups denounce him on websites and radio talkshows, he has not received abuse at public meetings; religious people tended not to turn up - "which in a way is a shame", he said.

What did he hope an atheist bloc in the US might achieve? "I would free children from being indoctrinated with the religion of their parents or their community. I would like to free everyone from the assumption you have to be religious in order to be a decent person or to be moral. Obviously stem cell research and all the interference with scientific research that goes on [should stop]. Obviously the whole creationist interference with education [should stop] but I think, more positively, I would like to see people encouraged to rejoice in the world in which they find themselves, the universe in which they have been born, to take full advantage of the tiny slice of eternity they have been granted."

He had been encouraged by the apparent distancing of Republican candidates for the 2008 presidential race from the Christian right. But he found "very depressing" the profession of faith from all the Democratic candidates. "I guess the Democrats have to pretend to be more pious than the Republicans because they are under suspicion of not being."

Darwin's Rottweiler

Richard Dawkins' vocal insistence on the pre-eminence of science (he is nicknamed Darwin's Rottweiler) and his rigorous attempts to dismantle notions of faith and belief have earned him many critics, from those who complain about his evangelising tone to those who confidently predict he will spend eternity in hellfire. His latest work, The God Delusion, incensed believers with its insistence on the hypocrisy and unreliability of scripture and its lampooning of creationists. It also annoyed some in the scientific community for suggesting that few top scientists believed in God and that separating the rational and the religious was intellectually impossible. In particular, Dawkins is angry at the way children are indoctrinated into faiths and takes issue with the unimpeachable taboos that protect religions from rational scrutiny.